Systematic Review and Meta-analysis of Randomized Clinical Trials Comparing Time-Restricted Eating With and Without Caloric Restriction for Weight Loss

Abstract

Context: Although it is well established that caloric restriction (CR) is the primary driver of weight loss, circadian-driven metabolic benefits have been recognized as possibly enhancing the effects of CR. Time-restricted eating (TRE) has emerged as a promising approach in this context.

Objective: We conducted a systematic review and meta-analysis to compare the effects of TRE with isocaloric diet controls (analysis 1) and non-isocaloric controls (analysis 2) on anthropometric and body-composition parameters in adults with overweight or obesity.

Data sources: A search was carried out in the Medline, LILACS, Embase, and CENTRAL databases using Medical Subject Heading (MeSH) and similar terms such as "Obesity," "Obesity, Abdominal," "Time-restricted eating," "Body weight," "Changes in body weight," and others.

Data extraction: We included 30 studies involving a total of 1341 participants. Studies were screened based on titles and abstracts followed by full-text reading, and data were extracted from eligible studies using a pre-established form. All these steps were performed by 2 authors independently and blinded, with discrepancies resolved by a third author.

Data analysis: The results of main findings revealed that, in studies using non-isocaloric controls, the TRE group showed significant reductions in body weight (BW) (mean difference [MD]: -2.82 kg; 95% CI: -3.49, -2.15), fat mass (FM) (MD: -1.36 kg; 95% CI: -2.09, -0.63), and fat-free mass (FFM) (MD: -0.86 kg; 95% CI: -1.23, -0.49). In studies that used isocaloric control strategies, the TRE group showed significant reductions in BW (MD: -1.46 kg; 95% CI: -2.65, -0.26), FM (MD: -1.50 kg; 95% CI: -2.77, -0.24), and FFM (MD: -0.41 kg; 95% CI: -0.79, -0. 03).

Conclusion: TRE yields favorable anthropometric and clinical outcomes, even when intake is isocaloric between the intervention and control groups. This result suggests that circadian effects may enhance the impact of CR on excess weight.

Systematic review registration: PROSPERO registration no. CRD42022301594.

Keywords: body weight; caloric restriction; obesity; time-restricted eating.